The “Edison” light was invented over a century ago. See U.S. Pat. No. 223,898 (1880); U.S. Pat. No. 317,631 (1885); and U.S. Pat. No. 438,310 (1890). The electric light bulb and socket transformed civilization.
Several alternative forms of lighting have become available since the Edison light, such as fluorescent lighting, used extensively to provide area lighting in offices, laboratories, and factories. More recently, light-emitting diodes (LEDs) are being used as a source of cooler, more energy-efficient light. LEDs are solid-state devices that emit light when direct current is applied across the diode's two terminals. LEDs are used for home and office lighting and instrumentation.
Because of the prevalence of Edison-light-based lighting, fluorescent light tubes, reformed as compact fluorescent tubes, and LEDs have been adapted to fit into Edison bulb bases to accelerate the adoption of these lighting sources. LEDs are also used in a wide range of instrumentation lighting applications where Edison light bulb and socket constraints are much less entrenched.
For most lamps, which is used herein to refer to lighting sources such as table lamps, ceiling lamps (including recessed ceiling lighting), and wall lamps, the Edison bulb continues to be used. The term lamp thus includes the light source with its attached lamp base and a lamp housing that connects the lamp base to a source of electrical current. The light source includes the partially translucent or transparent base that inserts into a lamp housing.
A lamp housing ranges from those that are mostly functional such as recessed ceiling-mounted “cans” with a decorative rim to cover the space between the can and the hole in the ceiling for the can, to a decorative, even highly decorative lamp housing, such as a Tiffany lamp. Electrical power is provided to a lamp housing via an electrical cord from a source of alternating electrical current such as a wall outlet, or via a two-wire power cord in the ceiling that is electrically connected to the lamp base through its housing. Two energized terminals inside the lamp housing serve to transfer electricity to the light source via the lamp base. The lamp base will have two electrical terminals, one terminal for each of the two electrical terminals in the lamp housing.
Compact fluorescent light sources and LED light sources have been adapted with a base that can be threaded into an Edison-type lamp housings and to use household alternating current to energize these light sources through the terminals in the lamp base, which include a first terminal in the center of the bottom of the lamp base and the metal threaded collar around the bottom of the lamp base.
The threading of the Edison housing and Edison lamp base serves two purposes. Threads holds the lamp base to the lamp housing. No clamp or fixture is used to hold one to the other. Also, the mating of the threaded lamp base and lamp housing completes the electrical circuit by using the metal threaded collar to complete one of the legs of the electrical circuit.
Other versions of the Edison socket and lamp base have been developed. For example, A. P. Buquor received two patents, U.S. Pat. No. 2,903,677 and U.S. Pat. No. 2,788,501, issued in 1957, use a magnetic connector to close and hold one leg of the circuit at the bottom of an otherwise Edison-type bulb base threaded to an Edison-type lamp housing.
There remains a need for better LED lighting fixtures that can be driven by more than one source of electrical current.